A sphere will break down at a voltage of 30,000 * r(cm) at sea level. A
cylinder of the same radius will break down at twice the voltage, if you can
protect the ends. The toroid neatly eliminates the end problem by
eliminating the ends, and the breakdown voltage will be the same as the
cylinder it's made from, minus a small kludge constant due to the major
curvature. So a toroid of 3" small diameter will break down at a little
lower than 300,000 volts at sea level. At higher altitudes, subtract 10%
from the breakdown voltage for every 2200 feet of altitude ASL up to about
two miles high. When any kind of breakout point is used, it's Katie bar the
door.
---Carl
-----Original Message-----
From: Phil
Sent: Thursday, July 10, 2014 5:12 AM
To: 'Tesla Coil Mailing List'
Subject: Re: [TCML] Topload imperfections
All,
Derek wrote:
Top loads will tend to break out at a voltage related to their
minor diameter.
Adding a breakout point will lower this breakout voltage, but I'm
sure we have all tried a breakout that was too small, the reduction in
breakout voltage can be aparently very small indeed
I can get almost the same length of streamers both with and without a BP,
but without needs 70 to 80% power on the variac before breakout, whereas
with a BP (a 12 inch rod) this can be 40% (on synchronous 200bps)
" We all try to make our toroids as smooth as possible and yet good
results can be had from finite element toroids.
To me, the above points to the field surrounding the torrioid
smoothing out the "lumps", be it a small breakout, a screw head on the
torroid or the coils of a finite element toroid."
I too prefer a nice smooth one, but borrowing a 50 inch toroid that has
regular construction joints around its edge, shows that completely smooth is
not a necessity. The toroid in question can be seen here.
http://www.hvtesla.com/images/upright.jpg
Also Kevin E's BIGGG coil has streamers that glide nicely from one side to
the other, despite its mesh construction, much like the toroid above is
capable of doing, so I think it's only a sharp projection that we should
avoid, which of course is nothing new as we all know.
As for the field created, I tried showing the effect of two different
toroid's fields (but on the same coil) on the streamer's behaviour.
Not conclusive because a larger toroid diameter automatically moves the
streamers further out anyway, but the video's second half, where the
streamer's boundaries have been superimposed on the video alongside one
another, clearly shows a difference.
https://www.youtube.com/watch?v=y6PTwVnb1uo
How smooth to top load need to be and is there a formulae that states
that a
sphere of diameter x on top of a sphere of diameter y as a combination,
will break out at a particular voltage?
Spheres will have a lot less effect surely - but probably more predictable.
" Am I right that the field smooths out imperfections?"
